An average of twice a day, a patient at the University of Maryland Medical Center has a heart attack, dangerous allergic reaction or other emergency that requires supplies from a crash cart.

The carts are the wheeled emergency stations that contain equipment including trays of life-saving drugs. And at Maryland, the trays are now also filled with radio-frequency identification tags that ensure all the medications are there and have not expired.

"We rely on these [carts] day in and day out," said Dr. John W. Blenko, an anesthesiologist at Maryland's Shock Trauma Center and an associate professor in Maryland's School of Medicine. "Every part of the hospital has one."

Maryland officials, looking for ways to improve efficiency and safety, rolled out the tags in April, he said.

RFID technology is well known in the retail industry, which uses tags to track inventory because individual items can be quickly counted with scanners. Some hospitals use the tags or bar codes to track other gear such as wheelchairs and beds, and some use technology to show when crash cart trays have been opened.

And while hospitals have been focusing more on reducing human error, Maryland appears to be the first to use the high-tech markers to track all its emergency medications.

Maryland doctors and pharmacists said so far, the tags appear to be spot on.

They are saving time for pharmacists, who are responsible for hundreds of crash cart trays, as well as daily medications for patients in the 750-bed center.

Until April, the pharmacist would manually inspect each tray, noting which drugs needed replacing and which were close to expiration. They'd write the information down on paper. Then someone else would double check the work, a 20-minute or so process.

A scanner now does the work. A tray is placed in the machine and seconds later a monitor lists what's missing or dated. All backup inventory is also tagged so managers can constantly identify which drugs are in short supply, a benefit at a time when many pharmacies are encountering manufacturing delays, said Adrianne Shepardson, manager of Maryland's Central Pharmacy Services.

When there is a substitute drug available, the tags allow pharmacists to quickly find and replace the old vials, she said.

There are nine different kinds of trays housed in carts scattered around the hospital, from the lobby to the pediatric centers to labor and delivery. Most trays have between 25 and 50 items, though a pediatric tray has 75 items, Shepardson said.

Pharmacists weren't exactly sure how many trays Maryland had or exactly how often they contained the wrong or expired medications.

"The average number of mistakes among hospitals is 2 in 1,000 and that's more than we liked," Shepardson said. "We're trying to build a robust system so we have no mistakes. This helps me sleep better at night."

She said pharmacists still must tag each vial, box or bag of drugs and visually inspect each tray and account for missing items. But the scanner has become a reliable double check, she said. Now that they are more confident in the system, officials are considering expanding the tags to operating room trays, she said.

When not being scanned, the small taped-on tags are "passive" or not energized or in operation, and stay out of the way, said Kevin MacDonald, who created the system along with partner Tim Kress-Spatz. The pair, co-founders of Washington-based Kit Check, spent nine months working on the system.

With backgrounds in software development and Wall Street trading, they saw a need for new technology in the pharmacy department of hospitals. MacDonald's wife had heard from a pharmacist friend about the 20-minute process of checking the trays.

"It baffled my mind that people here in 2012 are manually picking through kits and looking at 80 or 90 items and writing expiration dates on paper," he said. 'I said we had to create a new system."

The partners asked a dozen hospitals around the country if they could survey their trays and found almost 20 percent had expired items and eight percent had the wrong medications.

"Hospitals are really trying to cut down on errors," MacDonald said. "And they are looking to technology to help."